Lubricating oil, insulating and similar oil



Patented June 3, i943 U fl" LUBIRHCATING OIL, INSULATING AND SIMI- MR OIL itouis Al. Milreslra, Westfield, and Eugene lielier,

lLindlen, N. .l., assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application August 117, 1937, Serial No. 159,504

18 Claims.

This invention relates to an improvement in lubricating, insulating and similar oils. It particularly relates to the improvement of the stability of oils and prevents their decomposition, especially at elevated temperatures under the extreme oxidizing conditions existing in internal combustion engines, by the addition of oxidation inhibitors and sludge dispersers of the class of alkyl phosphites and aryl phosphites having the formula P('IR)a in which T represents sulphur, se lenium or tellurium and R represents an alkyl or an aryl radical.

Motor oils and other lubricants which are subjected to use at elevated temperatures show deterioration by oxidation, sludge formation and the like. Such deterioration may be checked and the lubricating oil considerably improved by the addition of certain oxidation inhibiting agents and the addition of agents for inhibiting ludge formation and the like. Thus it is already known that lubricating oils can be improved in respect to any particular property by the addition of small amounts of a particular substance. However, most of these agents which are useful for one particular purpose as, for instance, to inhibit oxidation, are undesirable in that such agents tend to increase undesirable characteristics of the oil in other respects as, for example, sludge formation.

In the present case an entirely new group of substances have been discovered which impart desirable oxidation inhibiting properties to a lubricating oil, thereby rendering it stable under all temperature conditions at which the lubricant is employed. This class of oxidation inhibitors not onlydoes not increase the sludge formation but it actually also acts as a sludge disperser.

These compounds are of the class of alkyl and aryl phozphites containing a member of the sulphur family as, for example, trihexyl thiophosphlte, triamyl thiophosphite, tributyl thiophosphite, triamyl selenothiophosphite, trialkyl tel lurophosphite, triphenyl thiophosphite, tritolyl thiophhosphite. trinaphthyl thiophosphite, or a mixture thereof. The alkyl radical may contain substituted groups as, for instance, chlorine, or the aryl radical may be alkylated with an alkyl group, containing preferably 3 to 12 carbon atoms in the alkyl group, as for example triamyl phenyl thiophosphite and tributyl phenyl thiophosphite, or the aryl radical may contain other substituted groups.

Compounds such as monoalkyl thiophosphites and dialkyl thiophosphites, as for example monoamyl thiophosphite, and dibutyl thiophosphite, are also satisfactory but it is preferred to use the trithio alkyl compounds. The preferred thiophosphite compounds are alkyl thiophosphites having from 3 to carbon atoms in the alkyl group, especially those having from 4 to 6 carbon atoms in the alkyl group and those alkyl thiophosphites which have boiling points above 125 C. These thiophosphites may also contain mixed alkyl groups such as monoamyl di-butyl thiophosphites and di-amyl monohexyl thiophosphites. A mixed alkyl aryl compound may be used as, for example, monoamyl diphenyl thiophosphite.

These compounds may be prepared by any of the well known methods. For example, an alkyl mercaptan such as amyl mercaptan may be reacted with phosphorous acid in the presence of hydrocarbon solvents at a temperature of about 150 C. and a pressure of one atmosphere. The thiophosphites may be separated from the reaction mixture by simply distilling off the solvents under reduced pressure, if necessary. One suitable method of preparing the thiophosphites is given by the following example:

A two-way flask was fitted with a dropping funnel and a return condenser. The flask was charged with 104 grams of amyl mercaptan and 230 cc. of ethylene iii-chloride, 4.0 grams of phosphorus trichloride was then slowly added through a dropping funnel, while refluxing the solution. The heating was continued for four hours at the end of which time the evolution of hydrochloric acid ceased. The solvent was removed by heating the reaction product at 100 C. under reduced pressure. Approximately to grams of the colorless amyl thiophosphite was recovered from the flask. This product was tested and gave a negative reaction to doctor solution, thus indicating that no free mercaptans were present.

The thiophosphites may also be prepared without the use of a solvent and compounds such as pyridine may be added to the mixture to increase the speed of the action. The crude thiophosphites may be further purified in any desired manner as, for example, by solvent extraction or distillation.

These thiophosphites, free from impurities, may be added to any type of mineral oil. The oil may be synthetic or a natural oil refined by any of the known methods as, for example, by acid,

alkali or clay treating by solvent extraction, hydrogenation or destructive hydrogenation, or by a combination of any of the foregoing. The alkyl thiophosphites give particularly desirable results when added to a lubricating oil of predominantly paraflinic nature.

The amount of the thiophosphite added may vary considerably with the character of the particular oil and may also vary depending upon the conditions under which the particular oil is to be subjected in operation. As little as 0.01% may be effective but it is preferred to use from 0.2% to 0.5% and as high as 5% may be used. As a general rule, it is found that 1% more or less gives satisfactory results. Other compounds may also groove milled out be included in the blend as, for instance. dyes, pour point depressors, oiliness agents, sludge dispersers and other ingredients.

An example of the present invention is shown by the following example:

Triamyl thiophosphite was blended with a well refined mineral oil S. A. E. 20 in the proportion of 0.2% and the following tests were run on the blend and on the blank oil not containing the triamyl thiophosphite:

Cone test A method for determining the tendency of an oil to deposit sludge matter upon a heated metallic surface. It consists in slowly dropping the oil to be tested over a heated metal cone which is generally steel. The coneis a circumferential in a screw fashion on the periphery thereby allowing a time of contact of about one minute between the heated steel surface and the oil. A total volume of 60 cc. of oil is released from a dropping funnel over a period of two hours. The temperature of the cone may be any desired value but for lubricating oils it is preferred to use about 250 C. since it represents approximately the extreme temperature to which oils are ordinarily exposed in the internal combustion engine. After the entire volume of oil is run overthe metallic surface the cone is washed with naphtha to completely remove the adhering 011 without disturbing the deposit left on the cone. The cone is then weighed and the increase in weight of the cone due to the deposit left thereon by the oil is expressed in milligrams.

Sligh test This determines the tendency of an oil to sludge under oxidizing conditions as described in the A. S. T. M. report committee D2, page 22, 1927, except that the time of run was increased from 2 hours to 24 hours in order to secure a more accurate test and comparison.

Lead tolerance This test is a measurement of the amount of lead oleate which may be added to a lubricant without causing it to assume definite corrosive properties when run on the Underwood corrosion testing apparatus. 7 The Underwood test is conducted as follows:

1500 cc. of the oil being treated is maintained at 325 F. and sprayed for hours against 2 each of copper-lead and cadmium-silver alloy bearings such as are used on automobile engines. The oil is circulated from a sump through a heating tube to a gear pump and thus by means of jets, maintained at a constant temperature on the 4 half bearings of cadmium-silver and copper-lead. The oil drippings from the bearings are recirculated. The bearings are weighed before and after the test to determine any loss in weight. The tests are then repeated with the addition of lead oleate in increments of 0.005% by weight (calculated as lead oxide). When the test re-' sults in the loss of weight equivalent to 1% of the weight of the bearing, the oil is said to be corrosive and it indicates that the lead tolerance of the oil has been exceeded and the amount of lead oxide added in the last previous test is regarded as the lead tolerance. By correlation of this test with the use of highly refined lubricating oil in actual operation of automobile engines under service conditions, it has been determined that a lead tolerance below 0.020 is unsatisfactory.

Oxidation rate Cone deposit, gr.

S. A. E. 20 mineral oil 0.40

A. E. 20 mineral oil 0.2% triamyl thiophosphite 0 22 Sligh No.

S. A. E. 20 mineral oil 39 S. A. E. 20 mineral oil 0.2% triamyl thiophosphite 37.7

Lead tolerance S. A. E. 20 mineral oil 0.005

S. A. E. 20 mineral oil 0.1%triamyl thiophosphite 0 030 Volume of oxygen absorbed, 10 cc. Sample, 15 minute interval at 200 C. S. A. E. 20 mineral oil 70 S. A. E. 20 mineral oil 0.2%

triamyl thiophosphite 88 56 40 The invention is not to be limited by any theory or method of operationbut only by the following claims in which it is desired to claim all novelty in so far as the prior art permits.

We claim:

1. An improved lubricant for use in internal combustion engines comprising a refined hydrocarbon oil containing an eifective concentration below about 1% of an oxidation inhibitor effective in preventing decomposition of said oil at the elevated temperatures encountered in lubricating internal combustion engines, said oxidation inhibitor being a compound of the class of organic phosphites containing an element selected from the class consisting of sulfur, selenium and tellurium, said element being attached directly to the phosphorus and the organic group, the organic radicals of the said organic phosphites having 3 to 20 carbon atoms in each radical and being selected from the grou consisting of alkyl radicals and halogen substituted alkyl radicals.

2. A lubricant according to claim 1 in which the oxidation inhibitor has the formula in which T represents an element selected from the group consisting of sulfur, selenium ant tellurium, and R1, R2, and R: represent organir radicals selected from the group consisting 01 alkyl radicals and halogenated substituted alky radicals.

3. A lubricant according to claim 1 in whicl the oxidation inhibitor has the formul P(T alkyl group) a, in which T represents a1 element selected from the group consisting o sulfur, selenium and tellurium.

4. An improved lubricant for use in interns combustion engines comprising a refined hydrocarbon oil containing 0.1 to 1% of an oxidation inhibitor effective in preventing decomposition of such oils at the elevated temperatures encountered in lubricating internal combustion engines, said oxidation inhibitor having the formula P(T alkyl group) 3, in which '1 represents an element selected from the group consisting of sulfur, selenium and tellurium, and in which the alky1 group contains from 4 to 6 carbon atoms.

5. An improved lubricant for use in internal combustion engines comprising a'refined hydrocarbon oil containing an effective concentration below about 1% of an oxidation inhibitor effective in preventing decomposition of said oil at the elevated temperatures encountered in lubricating internal combustion engines, said oxidation inhibitor having the formula P(S alkyl group)3, in which the alkyl group contains from 4 to 6 carbon atoms.

6. A lubricant according to claim 5 in which the concentration of the oxidation inhibitor is from 0.2 to 0.5%.

7. An improved lubricant for use in internal combustion engines comprising a refined hydrocarbon oil containing an effective concentration below about 1% of an oxidation inhibitor effective in preventing decomposition of said oil at the elevated temperatures encountered in lubricating internal combustion engines, said oxidation inhibitor having the formula P(S alkyl grouph, and 125 C.

8. A method of lubricating an internal combustion engine which comprises introducing into the crank case of said engine a refined hydrocarbon oil containing from 0.01 to 1% of an oxidation inhibitor of the formula in which T represents an element selected from the group consisting of sulfur, selenium and tellurium. and R1, R2, and R3 represent organic radicals having 3 to carbon atoms in each radical and selected from the group consisting of alkyl radicals and halogen substituted alkyl radicals.

9. A method of lubricating an internal combustion engine which comprises introducing into the crank case of said engine a refined hydro carbon oil containing from 0.2 to 0.5% of an oxidation inhibitor of the formula P(S alkyl grouph, in which the alkyl group contains from 4 to 6 carbon atoms.

10. A lubricating oil containing lead oleate in an amount sufflcient to corrode alloy bearings in the absence of an oxidation inhibitor. and an oxidation inhibitor in an amount sufficient to prevent such corrosion, said oxidation inhibitor having the formula 'ru. 1 m;

in which T represents an element selected from the group consisting of sulphur, selenium and tellurium, and R1, R2, and R: represent organic radicals each having 3 to 20 carbon atoms and having a boiling point above selected from the group consisting of alkyl radiacid which tends to cause corrosion of alloy bearings in the absence of an oxidation inhibitor, and an oxidation inhibitor in an amount sumcient to prevent such corrosion, said oxidation inhibitor having the formula TR; in which T represents an element selected from the group consisting of sulfur, selenium and tellurium, and R1, R2 and R3 represent organic radicals each having 3 to 20 carbon atoms and selected from the group consisting of alkyl radicals and halogen substituted alkyl radicals.

13. A lubricating oil containing a lead soap in an amount sufiicient to corrode alloy bearings in the absence of an oxidation inhibitor, and an oxidation inhibitor in an amount sufficient to prevent such corrosion, said oxidation inhibitor having the formula in which T represents an element selected from the group consisting of sulfur, selenium and tellurium, and R1, R2 and R3 represent organic radicals each having 3 to 20 carbon atoms and selected from the group consisting of alkyl radicals and halogen substituted alkyl radicals.

14. A lubricating oil containing a lead soap in an amount sufficient to corrode alloy bearings in the absence of an oxidation inhibitor, and triamyl thiophosphite in an amount sufiicient to prevent such corrosion.

15. An improved lubricant according to claim 7 in which each of the said alkyl groups of the oxidation inhibitor contains not more than 6 carbon atoms.

16. A lubricating oil non-corrosive to hard metal alloy bearings comprising a mineral lubricating oil normally corrosive to said bearings and an alkyl thiophosphite having 3 to 6 carbon atoms in each alkyl radical, said alkyl thiophosphite being added in a small but suflicient quanmy to inhibit the corrosion to said hard metal alloy bearing.

17. A lubricating oil as described in claim 16 in which the alkyl thiophosphite is tri-amyl trithiophosphite.

18. The method of preventing corrosion of bearing metal alloys selected from the group consisting of cadmium-silver alloys and copper-lead alloys in the presence of highly refined lubricating oils in internal combustion engines which comprises adding to said lubricating oils an alkyl thiophosphite having 3 to 6 carbon atoms in each alkyl radical in a small but suflicient amount to inhibit said corrosion.

LOUIS A. MIKESKA. EUGENE IIEBER. 

